1. Field of the Invention
The present invention relates to an expanding shoe drum brake and in particular to an improved expanding shoe drum brake of relatively heavy duty construction having improved means for return spring attachment and/or improved means for retaining the cam follower rollers.
2. Description of the Prior Art
Expanding shoe drum brakes, especially air or hydraulically actuated drum brake systems wherein arcuate brake shoes are secured to a portion of a wheeled vehicle and are pivotably rotated about an anchor member or members into engagement with a rotating annular brake drum for the purpose of retarding the velocity of the wheeled vehicle by the use of a brake actuating member, such as a displaceable cam element, are well known in the art. The brake actuating cam member, usually a rotatable cam element or a linearly movable wedge element, is located between the adjacent ends of the pivotal brake shoes and is secured to a rotatable cam shaft or to a linear actuation shaft, respectively, for translating oscillatory, generally linear motion from a power source, such as an air motor or the like, to the brake shoe.
The actuating member, often in the form of a so called "S" cam or a wedge, is usually located between cam or wedge followers, often in the form of rollers, rotatably fixed to the ends of the brake shoes.
Examples of such prior art cam actuated drum brakes may be seen by reference to U.S. Pat. Nos. 3,497,037; and 3,096,857 both of which are hereby incorporated by reference.
While the prior art cam and/or wedge actuated drum brakes, especially the "S"cam type drum brakes, are well received and accepted such prior art devices are not totally satisfactory in certain situations, especially when relatively heavy duty components such as return springs are utilized, as assembly of such heavy duty return springs to the brake shoes was often a difficult and time consumming task. Additionally, in certain heavy duty applications, it is important that the webs of the brake shoes be prevented from spreading and that the cam follower rollers be securely retained to the brake shoes but easily selectively removable therefrom. While the structures of the prior art devices were generally satisfactory for use in light weight and/or standard duty application drum brakes, when heavy duty components were utilized, such structures often did not provide the strength or did not provide the ease of assembly and disassembly which is considered desirable. Examples of such prior art structures may be seen by references to U.S. Pat. Nos. 2,928,506 and 3,275,103, both of which are hereby incorporated by reference.